Typical concrete highway construction consists of a plurality of concrete sections located within the same plane and joined at an expansion joint perpendicularly disposed to the longitudinal length of the sections. Elastic joint material is usually placed between the section ends to permit expansion and contraction of the sections during temperature variations, and it is known to use interlocking configurations at the highway section ends to prevent misalignment problems as the sections expand and contract under temperature fluctuations. It is also known to utilize dowel bars or pins between adjacent sections to aid in alignment.
Dowel bar arrangements for highway sections are typically shown in U.S. Pat. Nos. 2,127,973 and 2,262,677. Additional patents disclosing the use of joint divider plates and dowel bar systems are shown in U.S. Pat. Nos. Re. 24,921; 1,571,700; 1,987,392 and 2,106,095.
Proposals have been made to obviate some highway section joint problems by obliquely relating the joint line to the longitudinal length of the sections. Thus, with such an arrangement expansion of the sections produces slight lateral deflection of adjacent sections without imposing excessive compressive forces on the sections as to create "buckling" and destruction of the sections due to excessive compression. Examples of such high joint sections are shown in U.S. Pat. Nos. 1,279,431 and 2,280,455.
In the applicant's U.S. Pat. No. 3,972,640, a highway joint system is disclosed for concrete sections wherein a divider plate is obliquely disposed to the length of the section and dowel bars are located within the divider plate to aid in maintaining the alignment of the sections and return the sections toward the "normal" orientation as expanded and laterally deflected sections contract. In this patent dowel bars are disclosed which produce torsion forces to aid in returning the sections to normal alignment.
While the prior art devices have proposed various solutions to the maintaining of alignment of concrete highway sections without producing excessive compression forces, buckling, the opening of joints and similar problems, a concrete highway joint system has not yet been developed which meets all of the criteria of most highway departments, while being of an economically feasible construction.
It is an object of the invention to provide a concrete highway joint which is obliquely disposed to the length of the highway sections and which utilizes slab bolts of economical construction for maintaining alignment of the sections during expansion and contraction.
Another object of the invention is to provide a concrete highway joint which is obliquely disposed to the length of the highway sections wherein a tongue and groove relationship between the adjacent sections exists to resist section misalignment and relative vertical displacement, and wherein slab bolts embedded in adjacent sections extend through the joint and impose a biasing force on the sections to return the sections to alignment during contraction without permitting the joint to open.
An additional object of the invention is to provide a concrete highway joint which is obliquely disposed to the length of the highway sections wherein a plurality of slab bolts are mounted upon a separator plate, and the end regions of the slab bolts are embedded within the concrete of adjacent sections while a portion of the slab bolts' central region is provided with clearance with respect to the surrounding concrete permitting portions of the bolt to deform under bending forces to impose a biasing action on the sections for maintaining highway section alignment during expansion and contraction thereof.
A further object of the invention is to provide separator plate structure for a concrete highway joint system wherein the separator plate is of such configuration as to produce a keying tongue and groove relationship between adjacent sections, and the separator plate is supported on a base plate which can be disassembled from the separator plate during shipping, but is readily attachable thereto to permit support of the separator plate during pouring of the highway sections.
Another object of the invention is to provide a slab bolt for use with a concrete highway section joint wherein the bolts resist tension forces to a predetermined degree, and tension forces above such predetermined value overcome spring biasing means preventing excessive forces from being imposed upon the slab bolts to prevent the bolts from permanently stretching.
In the practice of the invention a separate plate having a V-shaped configuration is supported in a vertical manner by a base plate located at the separator plate lower edge. In an embodiment of the invention the base plate may be removably affixed to the separator plate to simplify shipping, and is assembled thereto at the site of use.
The separator plate is disposed obliquely to the length of the adjacent highway sections being poured, and a plurality of slab bolts are located along the length of the separator plate at its apex. The slab bolts include a central region disposed adjacent the separator plate, and end regions which are embedded within the concrete of adjacent highway sections. The central regions of the slab bolts on one side of the separator plate are encompassed within a yieldable tubular jacket as to provide a radial and axial clearance between a portion of the central region of the bolts with respect to the surrounding concrete permitting lateral bonding deformation of the bolts without harm to the concrete. Such bending deformation of the bolts imposes a biasing force between the highway sections interconnected by the slab bolts and such force will maintain the joint at its minimum closed dimension during temperature fluctuations preventing the joint from excessively opening, and the slab bolts will maintain the proper alignment of the sections for the given temperature conditions.
Each end region of the slab bolts is provided with a unit hereinafter designated as a "power cell", which, in the disclosed embodiment includes a shoulder plate disposed transversely to the length of the slab bolts and an abutment on the bolt ends axially locates the power cell thereon. The power cells permit tension forces to be transmitted to the slab bolts, but as the power cells are axially displaceable to a limited extent on the bolts and are axially biased by stiff spring elements, excessive tension forces imposed on the power cells, and bolts, causes axial displacement of the power cells to prevent permanent stretching of the slab bolts due to metal deformation beyond the yield point.
The concrete highway joint apparatus of the invention is relatively economical to manufacture, assemble and ship, and the use of the joint with an oblique joint orientation provides superior travel movement over the joint by vehicles and prevents excessive compression forces from occurring within the highway sections, and also prevents excessive opening of the highway joints during section contraction under cold temperature conditions.